Improved performance of copper interconnects
Copper (Cu) is now the preferred material for interconnections in ICs because it conducts better and lasts longer than aluminum. However, there are well-known problems with copper interconnects. Copper tends to migrate out of the wiring, degrading the operation of the IC. It can be corroded by exposure to oxygen and water. The phenomenon of electromigration can thin the copper interconnects, increasing their resistance and eventually breaking them, which lessens the useful life of the IC. Currently-used, tantalum-based barriers occupy volume of the wiring that should be filled with more conductive Cu, resulting in higher power consumption and slower operation of the IC. All these effects need to be countered to improve the performance of copper interconnects.
The invention, coupled with the invention in Harvard Case 3181, surround the copper with a superior protective barrier and stabilizing layer that solves the above-mentioned problems with Cu interconnects.
Case 3181 (see published PCT/US2009/37826, WO2009/117670) involves a new method of first depositing a conformal thin film of Mn (or Co, Cr or V) into the insulator walls of vias and trenches to form a self-aligned barrier of MnSixOy. Then standard technology is used to fill them with Cu. Finally, a similar metal film is deposited on top of a Cu-filled trench after a CMP step as a capping layer to adhere the Cu strongly to the next layer of Si3N4. Use of these barriers and adhesion layers should increase the speed and lifetime of ICs, while decreasing their power consumption.
Case 3631 ( US provisional filed October 2009) improves on the capping layer of case 3181 by adding a step before metal deposition that allows the metal deposition on Cu while preventing a metal layer from forming on the insulator. This process preserves the necessary properties of the insulator – a very desirable result. The new step involves reacting the surface after a CMP step with silane vapors. The silanes protect the insulator, but not the Cu, from deposition of the barrier and adhesion metal.
Intellectual Property Status: Patent(s) Pending
This invention, together with the invention from Harvard Case 3181, provides a more effective barrier around Cu interconnects which results in a longer living and faster functioning Integrated Circuits (ICs or chips) with lower power usage. Using commercially available precursor chemicals and deposition equipment, these methods can be readily adopted in standard CMOS manufacturing fabs.